Locking system for floorboards

ABSTRACT

The invention relates to a locking system for mechanical joining of floorboards ( 1, 1 ′), a floorboard having such a locking system and a flooring made of such floorboards. The locking system has mechanical cooperating means ( 36, 38; 6, 8, 14 ) for vertical and horizontal joining of adjoining floorboards. The means for horizontal joining about a vertical plane (F) comprise a locking groove ( 14 ) and a locking strip ( 16 ) which is located at opposite joint edge portions ( 4   a,    4   b ) of the floorboard ( 4 ). The locking strip ( 6 ) projects from the joint plane (F) and has an upwards projecting locking element ( 8 ) at its free end. The locking groove ( 14 ) is formed in the opposite joint edge portion ( 4   a ) of the floorboard at a distance from the joint plane (F). The locking groove ( 14 ) and the locking element ( 8 ) have operative locking surfaces ( 10, 11 ). The locking surfaces are essentially plane and spaced from the upper side of the projecting strip and inside the locking groove and make a locking angle (A) of at least 50° to the upper side of the board. Moreover the locking groove has a guiding part ( 12 ) for cooperation with a corresponding guiding part ( 6 ) on the locking element ( 8 ).

TECHNICAL FIELD

[0001] The invention generally relates to the field of mechanicallocking of floorboards. The invention relates to an improved lockingsystem for mechanical locking of floorboards, a floorboard provided withsuch an improved locking system, and a flooring made of suchmechanically joined floorboards. The invention generally relates to animprovement of a locking system of the type described and shown in WO9426999 and WO 9966151.

[0002] More specifically, the invention relates to a locking system formechanical joining of floorboards of the type having a core andpreferably a surface layer on the upper side of the core and a balancinglayer on the rear side of the core, said locking system comprising: (i)for horizontal joining of a first and a second joint edge portion of afirst and a second floorboard respectively at a vertical joint plane, onthe one hand a locking groove which is formed in the underside of saidsecond board and extends parallel with and at a distance from saidvertical joint plane at said second joint edge and, on the other hand, astrip integrally formed with the core of said first board, which stripat said first joint edge projects from said vertical joint plane andsupports a locking element, which projects towards a plane containingthe upper side of said first floorboard and which has a locking surfacefor coaction with said locking groove, and (ii) for vertical joining ofthe first and second joint edge, on the one hand a tongue which at leastpartly projects and extends from the joint plane and, on the other hand,a tongue groove adapted to coact with said tongue, the first and secondfloorboards within their joint edge portions for the vertical joininghaving coacting upper and coacting lower contact surfaces, of which atleast the upper comprise surface portions in said tongue groove and saidtongue.

FIELD OF APPLICATION OF THE INVENTION

[0003] The present invention is particularly suitable for mechanicaljoining of thin floating floors of floorboards made up of an uppersurface layer, an intermediate fibreboard core and a lower balancinglayer, such as laminate flooring and veneer flooring with a fibreboardcore. Therefore, the following description of the state of the art,problems associated with known systems, and the objects and features ofthe invention will, as a non-restricting example, focus on this field ofapplication and, in particular, on rectangular floorboards withdimensions of about 1.2 m * 0.2 m and a thickness of about 7-10 mm,intended to be mechanically joined at the long side as well as the shortside.

BACKGROUND OF THE INVENTION

[0004] Thin laminate flooring and wood veneer flooring are usuallycomposed of a core consisting of a 6-9 mm fibreboard, a 0.20-0.8 mmthick upper surface layer and a 0.1-0.6 mm thick lower balancing layer.The surface layer provides appearance and durability to the floorboards.The core provides stability and the balancing layer keeps the boardlevel when the relative humidity (RH) varies during the year. The RH canvary between 15% and 90%. Conventional floorboards of the type areusually joined by means of glued tongue-and-groove joints (i.e. jointsinvolving a tongue on a floorboard and a tongue groove on an adjoiningfloorboard) at the long and short sides. When laying the floor, theboards are brought together horizontally, whereby a projecting tonguealong the joint edge of a first board is introduced into a tongue groovealong the joint edge of the second adjoining board. The same method isused at the long side as well as the short side. The tongue and thetongue groove are designed for such horizontal joining only and withspecial regard to how glue pockets and gluing surfaces should bedesigned to enable the tongue to be efficiently glued within the tonguegroove. The tongue-and-groove joint presents coacting upper and lowercontact surfaces that position the boards vertically in order to ensurea level surface of the finished floor.

[0005] In addition to such conventional floors, which are connected bymeans of glued tongue-and-groove joints, floorboards have recently beendeveloped which are instead mechanically joined and which do not requirethe use of glue. This type of mechanical joint system is hereinafterreferred to as a “strip-lock system”, since the most characteristiccomponent of this system is a projecting strip which supports a lockingelement.

[0006] WO 9426999 and WO 9966151 (owner Välinge Aluminium AB) disclose astrip-lock system for joining building panels, particularly floorboards.This locking system allows the boards to be locked mechanically at rightangles to as well as parallel with the principal plane of the boards atthe long side as well as at the short side. Methods for making suchfloorboards are disclosed in EP 0958441 and EP 0958442 (owner VälingeAluminium AB). The basic principles of the design and the installationof the floorboards, as well as the methods for making the same, asdescribed in the four above-mentioned documents, are usable for thepresent invention as well, and therefore these documents are herebyincorporated by reference.

[0007] In order to facilitate the understanding and description of thepresent invention, as well as the comprehension of the problemsunderlying the invention, a brief description of the basic design andfunction of the known floorboards according to the above-mentioned WO9426999 and WO 9966151 will be given below with reference to FIGS. 1-3in the accompanying drawings. Where applicable, the followingdescription of the prior art also applies to the embodiments of thepresent invention described below.

[0008]FIGS. 3a and 3 b are thus a top view and a bottom viewrespectively of a known floorboard 1. The board 1 is rectangular with atop side 2, an underside 3, two opposite long sides with joint edgeportions 4 a, 4 b and two opposite short sides with joint edge portions5 a, 5 b.

[0009] Without the use of the glue, both the joint edge portions 4 a, 4b of the long sides and the joint edge portions 5 a, 5 b of the shortsides can be joined mechanically in a direction D2 in FIG. 1c, so thatthey join in a joint plane F (marked in FIG. 2c). For this purpose, theboard 1 has a flat strip 6, mounted at the factory, which strip extendsthroughout the length of the long side 4 a and which is made offlexible, resilient sheet aluminium. The strip 6 projects from the jointplane F at the joint edge portion 4 a. The strip 6 can be fixedmechanically according to the embodiment shown, or by means of glue, orin some other way. Other strip materials can be used, such as sheets ofother metals, as well as aluminium or plastic sections. Alternatively,the strip 6 may be made in one piece with the board 1, for example bysuitable working of the core of the board 1. The present invention isusable for floorboards in which the strip is integrally formed with thecore, and solves special problems appearing in such floorboards and themaking thereof. The core of the floorboard need not be, but ispreferably, made of a uniform material. However, the strip 6 is alwaysintegrated with the board 1, i.e. it is never mounted on the board 1 inconnection with the laying of the floor but it is mounted or formed atthe factory. The width of the strip 6 can be about 30 mm and itsthickness about 0.5 mm. A similar, but shorter strip 6′ is providedalong one short side 5 a of the board 1. The part of the strip 6projecting from the joint plane F is formed with a locking element 8extended throughout the length of the strip 6. The locking element 8 hasin its lower part an operative locking surface 10 facing the joint planeF and having a height of e.g. 0.5 mm. When the floor is being laid, thislocking surface 10 coacts with a locking groove 14 formed in theunderside 3 of the joint edge portion 4 b of the opposite long side ofan adjoining board 1′. The short side strip 6′ is provided with acorresponding locking element 8′, and the joint edge portion 5 b of theopposite short side has a corresponding locking groove 14′. The edge ofthe locking grooves 14, 14′ closest to the joint plane F forms anoperative locking surface 11 for coaction with the operative lockingsurface 10 of the locking element.

[0010] Moreover, for mechanical joining of both long sides and shortsides also in the vertical direction (direction D1 in FIG. 1c) the board1 is formed with a laterally open recess 16 along one long side (jointedge portion 4 a) and one short side (joint edge portion 5 a). At thebottom, the recess 16 is defined by the respective strips 6, 6′. At theopposite edge portions 4 b and 5 b there is an upper recess 18 defininga locking tongue 20 coacting with the recess 16 (see FIG. 2a).

[0011]FIGS. 1a-1 c show how two long sides 4 a, 4 b of two such boards1, 1′ on an underlay U can be joined together by means of downwardangling. FIGS. 2a-2 c show how the short sides 5 a, 5 b of the boards 1,1′ can be joined together by snap action. The long sides 4 a, 4 b can bejoined together by means of both methods, while the short sides 5 a, 5b—when the first row has been laid—are normally joined togethersubsequent to joining together the long sides 4 a, 4 b and by means ofsnap action only.

[0012] When a new board 1′ and a previously installed board 1 are to bejoined together along their long side edge portions 4 a, 4 b as shown inFIGS. 1a-1 c, the long side edge portion 4 b of the new board 1′ ispressed against the long side edge portion 4 a of the previous board 1as shown in FIG. 1a, so that the locking tongue 20 is introduced intothe recess 16. The board 1′ is then angled downwards towards thesubfloor U according to FIG. 1b. In this connection, the locking tongue20 enters the recess 16 completely, while the locking element 8 of thestrip 6 enters the locking groove 14. During this downward angling, theupper part 9 of the locking element 8 can be operative and provideguiding of the new board 1′ towards the previously installed board 1. Inthe joined position as shown in FIG. 1c, the boards 1, 1′ are locked inboth the direction D1 and the direction D2 along their long side edgeportions 4 a, 4 b, but the boards 1, 1′ can be mutually displaced in thelongitudinal direction of the joint along the long sides.

[0013]FIGS. 2a-2 c show how the short side edge portions 5 a and 5 b ofthe boards 1, 1′ can be mechanically joined in the direction D1 as wellas the direction D2 by moving the new board 1′ towards the previouslyinstalled board 1 essentially horizontally. Specifically, this can becarried out subsequent to joining the long side of the new board 1′ to apreviously installed board 1 in an adjoining row by means of the methodaccording to FIGS. 1a-1 c. In the first step in FIG. 2a, bevelledsurfaces adjacent to the recess 16 and the locking tongue 20respectively cooperate such that the strip 6′ is forced to movedownwards as a direct result of the bringing together of the short sideedge portions 5 a, 5 b. During the final bringing together, the strip 6′snaps up when the locking element 8′ enters the locking groove 14′, sothat the operative locking surfaces 10, 11 of the locking element 8′ andof the locking groove 14′ will engage each other.

[0014] By repeating the steps shown in FIGS. 1a-c and 2 a-c, the wholefloor can be laid without the use of glue and along all joint edges.Known floorboards of the above-mentioned type are thus mechanicallyjoined usually by first angling them downwards on the long side, andwhen the long side has been secured, snapping the short sides togetherby means of horizontal displacement of the new board 1′ along the longside of the previously installed board 1. The boards 1, 1′ can be takenup in the reverse order of laying without causing any damage to thejoint, and be laid again. These laying principles are also applicable tothe present invention.

[0015] For optimal function, subsequent to being joined together, theboards should be capable of assuming a position along their long sidesin which a small play can exist between the operative locking surface 10of the locking element and the operative locking surface 11 of thelocking groove 14. Reference is made to WO 9426999 for a more detaileddescription of this play. Such a play can be in the order of 0.01-0.05mm between the operative locking surfaces 10, 11 when pressing the longsides of adjoining boards against each other. However, there need not beany play at the upper edge of the joint edges at the upper side of thefloorboards.

[0016] In addition to what is known from the above-mentioned patentspecifications, a licensee of Välinge Aluminium AB, Norske Skog FlooringAS, Norway (NSF), introduced a laminated floor with mechanical joiningaccording to WO 9426999 in January 1996 in connection with the Domotextrade fair in Hannover, Germany. This laminated floor, which is shown inFIG. 4a and is marketed under the trademark Alloc®, is 7.2 mm thick andhas a 0.6-mm aluminium strip 6 which is mechanically attached on thetongue side. The operative locking surface 10 of the locking element 8has an inclination (hereinafter termed locking angle) of about 80° tothe plane of the board. The locking element has an upper rounded guidingpart and a lower operative locking surface. The rounded upper guidingpart, which has a considerably lower angle than the locking surface,contributes significantly to positioning of the boards in connectionwith installation and facilitating the sliding-in of the locking elementinto the locking groove in connection with angling and snap action. Thevertical connection is designed as a modified tongue-and-groove joint,the term “modified” referring to the possibility of bringing the tonguegroove and tongue together by way of angling.

[0017] WO 9747834 (owner Unilin Beeher B. V., the Netherlands) describesa strip-lock system which has a fibreboard strip and is essentiallybased on the above known principles. In the corresponding product,“Uniclic®”, which this owner began marketing in the latter part of 1997and which is shown in FIG. 4c, one seeks to achieve biasing of theboards. This results in high friction and makes it difficult to anglethe boards together and to displace them. The document shows severalembodiments of the locking system. All locking surfaces have an anglethat does not exceed 60° and the joint systems have no guiding surfaces.

[0018] Other known locking systems for mechanical joining of boardmaterials are described in, for example, GB-A-2,256,023 showingunilateral mechanical joining for providing an expansion joint in a woodpanel for outdoor use. The locking system does not allow joining of thejoint edges and is not openable by upward angling round the joint edges.Moreover the locking element and the locking groove are designed in away that does not provide sufficient tensile strength. U.S. Pat. No.4,426,820 (shown in FIG. 4e) which concerns a mechanical locking systemfor a plastic sports floor, which floor is intentionally designed insuch manner that neither displacement of the floorboards along eachother nor locking of the short sides of the floorboards by snap actionis allowed.

[0019] In the autumn of 1998, NSF introduced a 7.2-mm laminated floorwith a strip-lock system which comprises a fibreboard strip and ismanufactured according to WO 9426999 and WO 9966151. This laminatedfloor is marketed under the trademark “Fiboloc®” and has thecross-section illustrated in FIG. 4b.

[0020] In January 1999, Kronotex GmbH, Germany, introduced a 7.8 mmthick laminated floor with a strip lock under the trademark “Isilock®”.A cross-section of the joint edge portion of this system is shown inFIG. 4d. Also in this floor, the strip is composed of fibreboard and abalancing layer.

[0021] During 1999, the mechanical joint system has obtained a strongposition on the world market, and some twenty manufacturers have shown,in January 2000, different types of systems which essentially arevariants of Fiboloc®, Uniclic® and Isilock®. All systems have lockingsurfaces with low locking angles and the guiding, in the cases where itoccurs, is to be found in the upper part of the locking element.

SUMMARY OF THE INVENTION

[0022] Although the floors according to WO 9426999 and WO 99/66151 andthe floor sold under the trademark Fiboloc® exhibit major advantages incomparison with traditional, glued floors, further improvements aredesirable mainly in thin floor structures.

[0023] The vertical joint system, which comprises locking elements andlocking grooves, has two coacting parts, viz. a locking part withoperative locking surfaces which prevent the floorboards from slidingapart, and a guiding part, which positions the boards and contributes tothe locking element being capable of being inserted into the lockinggroove. The greater the angular difference between the locking surfaceand the guiding part, the greater the guiding capacity.

[0024] The preferred embodiment of the locking element according to WO9426999, having a rounded upper part and an essentially perpendicularlower locking surface, is ideal for providing a joint of high strength.The inward angling and snapping-in function is also very good and can beachieved with completely tight joint edges owing to the fact that thestrip is bent downwards, whereby the locking element opens and snapsinto the locking groove.

[0025] The drawback of this design of the locking element is thetaking-up function, which is a vital part in most mechanical lockingsystems. The locking groove follows a circular arc with its centre in anupper joint edge (i.e. where the vertical joint plane intersects theupper side of the floorboard). If the locking groove has a locking anglecorresponding to the tangent to the circular arc, below referred to asclearance angle, taking-up can be carried out without problems. If thelocking angle is greater than the clearance angle, the parts of thelocking system will overlap each other in upward angling, which makesthe taking-up considerably more difficult.

[0026] Alloc® (see FIG. 4a) has an aluminium strip with a locking angleof about 80° and a clearance angle of about 65°. The other known systemswith strips made integrally with the core of the floorboard have lockingangles and clearance angles of 30-55° owing to the width of the stripbeing narrower and the radius of the circular arc being smaller. Thisresults in low tensile strength in the horizontal direction D2 since thelocking element easily slides out of the locking groove. Moreover, thehorizontal tensile stress will be partly converted into an upwardlydirected force which may cause the edges to rise. This basic problemwill now be explained in more detail.

[0027] When the relative humidity, RH, changes from about 80% in summerto about 20% in winter, the floating floor shrinks by about 10 mm in anormal room. The motion takes place in a concealed manner under theskirting board at the surrounding walls. This shrinkage will move allfurniture which exerts a load onto the floor. Tests have shown that if aroom is fitted with heavy bookcases along the walls, the joint will besubjected to very high load or tensile stress in winter. At the longside this load may amount to about 300 kg/running metre of joint. At theshort side where the load is distributed over a smaller joint width, theload may amount to 500 kg/running metre.

[0028] If the locking surfaces have a low locking angle, the strength ofthe joint will be reduced to a considerable extent. In winter the jointedges may slide apart so that undesirable visible joint gaps arise onthe upper side of the floor. Besides, the angled locking surface of thelocking element will press the upper locking surface of the lockinggroove upwards to the joint surface. The upper part of the tongue willpress the upper part of the tongue groove upwards, which results inundesirable rising of the edges. The present invention is based on theunderstanding that these problems can be reduced to a considerableextent, for example, by making the locking surfaces with high lockingangles exceeding 50° and, for instance, by the locking surfaces beingmoved upwards in the construction. The ideal design is perpendicularlocking surfaces. Such locking surfaces, however, are difficult to open,especially if the strip is made of fibreboard and is not as flexible asstrips of e.g. aluminium.

[0029] Perpendicular locking surfaces can be made openable ifinteraction between a number of factors is utilised. The strip should bewide in relation to the floor thickness and it should have goodresilience. The friction between the locking surfaces should beminimised, the locking surface should be small and the fibre material inthe locking groove, locking element and upper joint edges of the lockingsystem should be compressible. Moreover, it is advantageous if theboards in the locked position can assume a small play of a fewhundredths of a millimetre between the operative locking surfaces of thelocking groove and the locking element if the long side edge portions ofthe boards are pressed together.

[0030] There are today no known products or methods which givesufficiently good solutions to problems which are related to essentiallyperpendicular locking surfaces which are at the same time easy to open.

[0031] It would be a great advantage if openable locking surfaces couldbe made with greater degrees of freedom and a high locking angle,preferably 90°, in combination with narrow strips which reduce waste inconnection with working. The manufacture would be facilitated sinceworking tools would only have to be guided accurately in the horizontaldirection and the joint would obtain high strength.

[0032] To sum up, there is a great need for providing a locking systemwhich takes the above-mentioned requirements, problems and desideratainto consideration to a greater extent than prior art. The inventionaims at satisfying this need.

[0033] An object of the present invention therefore is to provide alocking system having

[0034] (i) locking surfaces with a high locking angle and high strength,

[0035] (ii) a horizontal joint system which has such locking surfacesand which at the same time is openable, and

[0036] (iii) a horizontal joint system which has such locking surfacesand at the same time comprises guiding parts for positioning of thefloorboards.

[0037] The invention is based on a first understanding that theidentified problems must essentially be solved with a locking systemwhere the locking element has an operative looking surface in its upperpart instead of in its lower part as in prior-art technique. When takingup an installed floor by upward angling, the locking surface of thelocking groove will therefore exert a pressure on the upper part of thelocking element. This results in the strip being bent backwards anddownwards and the locking element being opened in the same way as ininward angling. In a suitable design of locking element and lockinggroove, this pressure can be achieved in a part of the locking elementwhich is closer to the top of the locking element than that part of thelocking element which is operative in the locked position. In this way,the opening force will be lower than the locking force.

[0038] The invention is also based on a second understanding which isrelated to the motions during upward angling and taking-up of aninstalled floor. The clearance angling, i.e. the tangent to a circulararc with its centre where the vertical joint plane intersects the upperside of the floorboard, is higher in the upper part of the lockingelement than in its lower part. If a part of the locking surface, whichin prior-art technique is placed in the lower part of the lockingelement and the locking groove respectively, is placed in the upper partinstead according to the invention, the difference in degree between thelocking angle and the clearance angle will be smaller, and the openingof the locking when taking up an installed floor will be facilitated.

[0039] The invention is also based on a third understanding which isrelated to the guiding of the floorboards during inward angling when thefloor is to be laid. Guiding is of great importance in inward angling ofthe long sides of the floorboards since the floorboards have oftenwarped and curved and therefore are somewhat arcuate or in the shape ofa “banana”. This shape of a banana can amount to some tenths of amillimetre and is therefore not easily visible to the naked eye in afree board. If the guiding capacity of the locking system exceeds themaximum banana shape, the boards can easily be angled downwards, andthey need not be pressed firmly against the joint edge in order tostraighten the banana shape and allow the locking element to be insertedinto the locking groove. In prior-art locking systems, the guiding partis formed essentially in the upper part of the locking element, and ifthe locking surface is moved up to the upper part, it is not possible toform a sufficiently large guiding part. A sufficiently great and aboveall more efficient and reliable guiding is achieved according to theinvention by the guiding part being moved to the locking groove and itslower part. According to the invention it is even possible to form theentire necessary guiding in the lower part of the locking groove. Inpreferred embodiments, coacting guiding parts can also be formed both inthe upper part of the locking element and the lower part of the lockinggroove.

[0040] According to a first aspect of the invention, a locking system isprovided of the type which is stated by way of introduction and whichaccording to the invention is characterised by the combination that thelocking element has at least one operative locking surface which ispositioned in the upper part of the locking element, that this operativelocking surface is essentially plane and in relation to the plane of theboards has an angle (A) which exceeds 50°, that the locking groove hasat least one locking surface which is essentially plane and whichcooperates with said locking surface of the locking element, that thelocking groove has a lower inclined or rounded guiding part which guidesthe locking element into the locking groove by engagement with a portionof the locking element which is positioned above the locking surface ofthe locking element or adjacent to its upper edge.

[0041] The invention concerns a locking system for mechanical joining offloorboards and a floorboard having such a locking system. The lockingsystem has mechanical cooperating means for vertical and horizontaljoining of adjoining floorboards. The means for horizontal joining abouta vertical joint plane comprise a locking groove and a locking stripwhich are positioned at the opposite joint edge portions of thefloorboard. The locking strip extends from the joint plane and has anupwardly projecting locking element at it free end. The locking grooveis formed in the opposite joint edge portion of the floorboard at adistance from the joint plane. The locking groove and the lockingelement have operative locking surfaces. These locking surfaces areessentially plane and positioned at a distance from the upper side ofthe projecting strip and in the locking groove and form an angle of atleast 50° to the upper side of the board. Moreover, the locking groovehas a guiding part for cooperation with a corresponding guiding part ofthe locking element.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042]FIGS. 1a-c show in three stages a downward angling method formechanical joining of long sides of floorboards according to WO 9426999.

[0043]FIGS. 2a-c show in three stages a snap-action method formechanical joining of short sides of floorboards according to WO9426999.

[0044]FIGS. 3a-b are a top plan view and a bottom view respectively of afloorboard according to WO 9426999.

[0045]FIGS. 4a-e show four strip-lock systems available on the marketand a strip-lock system according to U.S. Pat. No. 4,426,820.

[0046]FIG. 5 shows in detail the basic principles of a known strip-locksystem for joining of the long sides of floorboards according to WO9966151.

[0047]FIG. 6 shows a variant of a locking system (applicant VälingeAluminium AB) for which protection is sought and which has not yet beenpublished.

[0048] FIGS. 7+8 illustrate a locking system according the invention.

[0049]FIG. 9 shows another example of a floorboard and a locking systemaccording to the present invention.

[0050] FIGS. 10-12 show variants of a locking groove and a lockingcomponent of three further examples of a floorboard and a locking systemaccording to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0051] Prior to the description of preferred embodiments, with referenceto FIG. 5, a detailed explanation will first be given of the mostimportant parts in a strip lock system.

[0052] The invention can be applied in joint systems with a worked stripwhich is made in one piece with the core of the board, or with a stripwhich is integrated with the core of the board but which has been madeof a separate material, for instance aluminium. Since the workedembodiment, where strip and core are made of the same material,constitutes the greatest problem owing to higher friction and poorerflexibility, the following description will focus on this field ofapplication.

[0053] The cross-sections shown in FIG. 5 are hypothetical, notpublished cross-sections, but they are fairly similar to the lockingsystem of the known floorboard “Fiboloc®” and to the locking systemaccording to WO 9966151. Accordingly, FIG. 5 does not represent theinvention but is only used a starting point of a description of thetechnique for a strip lock system for mechanical joining of adjoiningfloorboards. Parts corresponding to those in the previous Figures are inmost cases provided with the same reference numerals. The construction,function and material composition of the basic components of the boardsin FIG. 5 are essentially the same as in embodiments of the presentinvention, and consequently, where applicable, the following descriptionof FIG. 5 also applies to the subsequently described embodiments of theinvention.

[0054] In the embodiment shown, the boards 1, 1′ in FIG. 5 arerectangular with opposite long side edge portions 4 a, 4 b and oppositeshort side edge portions 5 a, 5 b. FIG. 5 shows a vertical cross-sectionof a part of a long side edge portion 4 a of the board 1, as well as apart of a long side edge portion 4 b of an adjoining board 1′. Theboards 1 have a core 30 which is composed of fibreboard and whichsupports a surface layer 32 on its front side (upper side) and abalancing layer 34 on its rear side (underside). A strip 6 is formedfrom the core and balancing layer of the floorboard by cutting andsupports a locking element 8. Therefore the strip 6 and the lockingelement 8 in a way constitute an extension of the lower part of thetongue groove 36 of the floorboard 1. The locking element 8 formed onthe strip 6 has an operative locking surface 10 which cooperates with anoperative locking surface 11 in a locking groove 14 in the opposite longside edge portion 4 b of the adjoining board 1′. By the engagementbetween the operative locking surfaces 10, 11 a horizontal locking ofthe boards 1, 1′ transversely of the joint edge (direction D2) isobtained. The operative locking surface 10 of the locking element 8 andthe operative locking surface 11 of the locking groove 14 form a lockingangle A with a plane parallel with the upper side of the floorboards.This locking angle A of 60° corresponds to the tangent to a circular arcC which has its centre in the upper joint edge, i.e. the intersectionbetween the joint plane F and the upper side of the boards, and whichpasses the operative locking surfaces 10, 11. In upward angling of thefloorboard 1′ relative to the floorboard 1, the locking groove willfollow the circular arc C, and taking-up can therefore be made withoutresistance. The upper part of the locking element has a guiding part 9,which in installation and inward angling guides the floorboard to thecorrect position.

[0055] To form a vertical lock in the D1 direction, the joint edgeportion 4 a has a laterally open tongue groove 36 and the opposite jointedge portion 4 b has a laterally projecting tongue 38 which in thejoined position is received in the tongue groove 36. The upper contactsurfaces 43 and the lower contact surfaces 45 of the locking system arealso plane and parallel with the plane of the floorboard.

[0056] In the joined position according to FIG. 5, the two juxtaposedupper portions 41 and 42 of the surfaces, facing each other, of theboards 1, 1′ define a vertical joint plane F.

[0057]FIG. 6 shows an example of an embodiment according to theinvention, which has not yet been published and which differs from theembodiment in FIG. 5 by the tongue 38 and the tongue groove 36 beingdisplaced downwards in the floorboard so that they are eccentricallypositioned. Moreover, the thickness of the tongue 38 (and, thus, thetongue groove 36) has been increased while at the same time the relativeheight of the locking element 8 has been retained. Both the tongue 38and the material portion above the tongue groove 36 are thereforesignificantly more rigid and stronger while at the same time the floorthickness T, the outer part of the strip 6 and the locking element 8 areunchanged.

[0058]FIG. 7 shows a first embodiment of the present invention. Thelocking element 8 has a locking surface 10 with a locking angle A whichis essentially perpendicular to the plane of the floorboards. Thelocking surface 10 has been moved upwards relative to the upper side ofthe strip 6, compared with prior-art technique.

[0059] The locking angle A in this embodiment of the invention isessentially greater than a clearance angle TA, which corresponds to thetangent to a circular arc C1 which is tangent to the upper part of thelocking element 8 and which has it centre C3 where the joint plane Fintersects the upper side of the boards.

[0060] Since the edge of the locking groove 14 closest to the jointplane F has portions which are positioned outside the circular arc C1 tobe able to retain the locking element 8 in the locking groove, theseportions will, in taking-up of the floorboard 1′, follow a circular arcC2 which is concentric with and has a greater diameter than the circulararc C1 and which intersects the lower edge of the operative lockingsurface 11 of the locking groove. Taking-up of the floorboard 1′ byupward angling requires that the strip 6 can be bent or that thematerial of the floorboards 1, 1′ can be compressed.

[0061] In a preferred embodiment of the invention, the boundary surfaceof the locking groove 14 closest to the joint plane F has a lowerguiding part 12 which is positioned inside the circular arc C1 and whichwill therefore efficiently guide the locking element 8 in connectionwith the laying of the floor and the downward angling of the floorboard1′ relative to the floorboard 1.

[0062]FIG. 7 also shows that the operative locking surface 11 of thelocking groove 14 and the operative locking surface 10 of the lockingelement 8 have been moved upwards in the construction and are located ata distance from the upper side of the locking strip 6. This positioningbrings several advantages which will be discussed in the following.

[0063] As is also evident from FIG. 7, there is an inclined surface 13between the upper side of the locking strip 6 and the lower edge of theoperative locking surface 10 of the locking element 8. In this shownembodiment, there is a gap between this inclined surface 13 and theguiding part 12 of the locking groove 14, so that the transition of theguiding part to the underside of the edge portion 4 b is located insidethe circular arc C1. Owing to such a gap, the friction is reduced inmutual displacement of the floorboards along the joint plane F inconnection with the laying of the floor.

[0064]FIG. 8 shows how upward angling can take place when taking up aninstalled floor. The locking surface 11 of the locking groove exerts apressure on the upper part of the operative locking surface 10 of thelocking element 8. This pressure bends the strip 6 downwards and thelocking element 8 backwards and away from the joint plane F. Inpractice, a marginal compression of the wood fibres in the upper jointedge surfaces 41, 42 of the two floorboards and of the wood fibres inthe locking surface 10 of the locking element and the locking surface 11of the locking groove takes place. If the joint systems are besidesdesigned in such manner that the boards in their locked position canassume a small play of some hundredths of a millimetre between thelocking surfaces 10, 11, opening by upward angling can take place asreliably and with the same good function as if the locking surfaces wereinclined.

[0065]FIG. 9 shows another embodiment of the invention. In thisembodiment, the groove 36 and the tongue 38 have been made shorter thanin the embodiment according to FIGS. 7 and 8. As a result, themechanical locking of two adjoining floorboards 1, 1′ can be carried outboth by vertical snap action and by inward angling during the bending ofthe strip. The vertical snap action can also be combined with knownshapes of locking surfaces and with a possibility of displacement alongthe joint direction in the locked position and also taking-up by pullingout along the joint edge or upward angling. However, the Figure showsthe floorboards during inward angling of the floorboard 1′. The lowerpart or guiding part 12 of the locking groove guides the floorboards andenables the introduction of the locking element 8 into the lockinggroove 14 so that the locking surfaces 10, 11 will engage each other.The strip 6 is bent downwards and the locking element 8 is guided intothe locking groove although the edge surface portions 41, 42, facingeach other, of the floorboards are spaced apart. The locking angle A isin this embodiment about 80°. The bending of the strip can befacilitated by working the rear side of the strip, so that a part of thebalancing layer 34 between the joint plane F and the locking element 8is wholly or partly removed.

[0066]FIG. 10 shows an enlargement of the locking element 8 and thelocking groove 14. The locking element 8 has an operative upper lockingsurface 10 which is formed in the upper part of the locking element at adistance from the upper side of the locking strip 6. The locking groove14 has a cooperating operative locking surface 11 which has also beenmoved upwards and which is at a distance from the opening of the lockinggroove 14.

[0067] Operative locking surfaces relate to the surfaces 10, 11 which,when locked and subjected to tension load, cooperate with each other.Both surfaces are in this embodiment plane and essentially at rightangles to the principal plane of the floorboards. The locking groove hasa guiding part 12 which is located inside the previously mentionedcircular arc C1 and which in this embodiment is tangent to the upperpart of the operative locking surface 10 of the locking element 8.

[0068] In this embodiment, the locking element has in its upper part aguiding part 9 which is located outside the circular arc C1. The guidingparts 9, 12 of the locking element and the locking groove respectivelycontribute to giving the joint system a good guiding capacity. The totallateral displacement of the floorboards 1, 1′ in the final phase of thelaying procedure is therefore the sum of E1 and E2 (see FIG. 10), i.e.the horizontal distance between the lower edge of the guiding part 12and the circular arc C1 and between the upper edge of the guiding part 9and the circular arc C1. This sum of E1 and E2 should be greater thanthe above-mentioned maximum banana shape of the floorboards. For thejoint system to have a guiding capacity, E1 and E2 must be greater thanzero, and both E1 and E2 can have negative values, i.e. be positioned onthe opposite side of the circular arc C1 relative to that shown in theFigure.

[0069] The guiding capacity is further improved if the strip 6 isbendable downwards and if the locking element 8 is bendable away fromthe joint plane so that the locking surface 10 of the locking elementcan open when the locking element comes into contact with a part of theother board. A free play between surfaces which are not operative in thelocking system facilitates manufacture since such surfaces need not beformed with narrow tolerances. The surfaces which are operative in thelocking system and which are intended to engage each other in the laidfloor, i.e. the operative locking surfaces 10, 11, the edge surfaceportions 41, 42 and the upper contact surfaces 43 between the groove 36and the tongue 38 must, however, be manufactured with narrow tolerancesboth as regards configuration and as regards their relative positions.

[0070] If the inoperative surfaces in the locking system are spaced fromeach other, the friction in connection with lateral displacement ofjoined floorboards along the joint edge will decrease.

[0071] According to the invention, the operative locking surfaces 10, 11of the locking element and in the locking groove have been formed with asmall height, seen perpendicular to the principal plane of thefloorboards. This also reduces the friction in lateral displacement ofjoined floorboards along the joint edge.

[0072] By the operative locking surfaces according to the inventionbeing made essentially plane and parallel with the joint plane F, thecritical distance between the joint plane F and the locking surface 10and 11, respectively, can easily be made with very high precision, sincethe working tools used in manufacture need only be controlled with highprecision essentially horizontally. The tolerance in the verticaldirection only affects the height of the operative locking surfaces butthe height of the locking surfaces is not as critical as their positionin the horizontal direction. Using modern manufacturing technique, thelocking surface can be positioned in relation to the joint plane with atolerance of ±0.01 mm. At the same time the tolerance in the verticaldirection can be ±0.1 mm, which results in, for instance, the height ofthe operative locking surfaces varying between 0.5 mm and 0.3 mm.Tensile tests have demonstrated that operative locking surfaces with aheight of 0.3 mm can give a strength corresponding to 1000 kg/runningmetre of joint. This strength is considerably higher than required in anormal floor joint. The height H of the locking element 8 above theupper side of the strip 6 and the width W of the locking element 8 on alevel with the operative locking surface are important to the strengthand the taking-up of the floorboards.

[0073] At the long side where the strength requirements are lower, thelocking element can be made narrower and higher. A narrow lockingelement bends more easily and facilitates removal of installedfloorboards.

[0074] At the short side where the strength requirements areconsiderably higher, the locking element should be low and wide. Thelower front part 13 of the locking element, i.e. the locking elementportion between the lower edge of the locking surface 10 and the upperside of the strip 6, has in this embodiment an angle of about 45°. Sucha design reduces the risk of cracking at the border between the upperside of the strip 6 and the locking element 8 when subjecting theinstalled floor to tensile load.

[0075]FIG. 11 shows another embodiment of the invention. In this case,use is made of a locking element 8 which has an upper operative lockingsurface 10 with an angle of about 85° which is greater than theclearance angle, which is about 75°. In this embodiment, the guidingpart 12 of the locking groove 14 is also used as a secondary lockingsurface which supplements the operative locking surfaces 10, 11. Thisembodiment results in very high locking forces. The drawback of thisembodiment, however, is that the friction in connection with relativedisplacement of the floorboards 1, 1′ in the lateral direction along thejoint plane F will be considerably greater.

[0076]FIG. 12 shows one more embodiment with essentially perpendicularlocking surfaces 10, 11 and small guiding parts 9, 12, which makes itnecessary to bend the strip 6 in connection with laying of thefloorboards. The joint system is very convenient for use at the shortsides of the floorboards where the need for guiding is smaller since inpractice there is no “banana shape”. Opening of the short side can beeffected by the long sides first being angled upwards, after which theshort sides are displaced in parallel along the joint edge. Opening canalso be effected by upward angling if the locking groove and the lockingelement have suitably designed guiding parts 12, 9 which are rounded orwhich have an angle less than 90°, and if the operative locking surfaces10, 11 have a small height LS (FIG. 12), so that their height is lessthan half the height of the locking element. In this embodiment, E2 isgreater than E1, which makes the sum of E2 and E1 greater than zero (E1represents in this case a negative value). If in this case E1 and E2should be of almost the same size, the guiding may be effected bydownward bending of the strip 6, which automatically causes displacementof the guiding part 9 of the locking element 8 away from the intendedjoint plane F and also causes a change in angle of the locking element 8so that guiding takes place.

[0077] Several variants of the invention are feasible. The joint systemcan be manufactured with a large number of different joint geometries,some or all of the above parameters being made different, especiallywhen it is desirable to give priority to a certain property over theother properties.

[0078] The owner has taken into consideration and tested a number ofvariants based on that stated above.

[0079] The height of the locking element and the angle of the lockingsurfaces can be varied. Nor is it necessary for the locking surface ofthe locking groove and the locking surface of the locking element tohave the same inclination or configuration. Guiding parts can be madewith different angles and radii. The height of the locking element canvary over its width in the principal plane of the floorboard, and thelocking element can have different widths at different levels. The sameapplies to the locking groove. The locking surface of the locking groovecan be made with a locking angle exceeding 90° or be made slightlyrounded. If the locking surfaces of the locking element is made with anangle exceeding 90°, taking-up of the floorboards by upward angling canbe prevented and permanent locking can be achieved. This can also beachieved with a joint system having 90° locking surfaces which aresufficiently large or in combination with specially designed guidingparts which counteract upward angling. Such locking systems areparticularly suited for short sides which require a high locking force.

1. A locking system for mechanical joining of floorboards (1, 1′) havinga core (30) and opposite first and second joint edge portions (4 a, 5 aand 4 b, 5 b, respectively), adjoining floorboards (1, 1′) in themechanically joined position having their first and second joint edgeportion (4 a, 5 a and 4 b, 5 b, respectively) joined at a vertical jointplane (F), said locking system comprising a) for vertical joining of thefirst joint edge portion (4 a) of a first floorboard (1) and the secondjoint edge portion (4 a, 5 a and 4 b, 5 b, respectively), of anadjoining second floorboard (1′), mechanical cooperating means (36, 38),and b) for horizontal joining of the first and second joint edgeportions (4 a, 5 a and 4 b, 5 b, respectively), mechanical cooperatingmeans (6, 8; 14) which comprise a locking groove (14) formed in theunderside (3) of said second floorboard (1′) and extending parallel withand at a distance from the vertical joint plane (F) at said second jointedge portion (4 b, 5 b) and having a downward directed opening, and astrip (6) integrally formed with the core of said first floorboard (1),which strip at said first joint edge portion (4 a, 5 a) projects fromsaid vertical joint plane (F) and at a distance from the joint plane (F)has a locking element (8) which projects towards a plane containing theupper side of said first floorboard (1) and which has at least oneoperative locking surface (10) for coaction with said locking groove(14), the locking groove (14), seen in the plane of the floorboards andaway from the vertical joint plane, (F) having a greater width than saidlocking element (8), characterised by the combination that said at leastone operative locking surface (10) of the locking element (8) isessentially plane and located at the upper part of the locking elementat a distance from the upper side of the projecting strip (6) and facesthe joint plane (F), that the locking groove (14) has at least oneessentially plane operative locking surface (11) which is located in thelocking groove at a distance from the opening of the locking groove andwhich is designed to cooperate with said locking surface (10) of thelocking element (8) in the joined position, that the locking groove (14)at the lower edge closest to the joint plane (F) has an inclined orrounded guiding part (12) which extends from the locking surface (11) ofthe locking groove and to the opening of the locking groove and which isintended to guide the locking element (8) into the locking groove (14)by engaging a portion of the locking element (8) which is positionedabove the locking surface (10) of the locking element or adjacent to itsupper edge, that said operative locking surfaces (10 and 11,respectively) of the locking element (8) and the locking groove (14)make a locking angle (A) of at least 50° to the upper side of theboards.
 2. A locking system as claimed in claim 1, characterised in thatthe floorboards (1, 1′) have a core (30), a surface layer (32) on theupper side of the core and a balancing layer (34) on the rear side ofthe core (30).
 3. A locking system as claimed in claim 1, characterisedin that the operative locking surfaces (10 and 11, respectively) of thelocking element (8) and the locking groove make an angle (A) of at least60° to the upper side of the boards (1, 1′).
 4. A locking system asclaimed in claim 3, characterised in that the operative locking surfaces(10 and 11, respectively) of the locking element (8) and the lockinggroove make an angle (A) of at least 80° to the upper side of the boards(1, 1′).
 5. A locking system as claimed in claim 4, characterised inthat the operative locking surfaces (10 and 11, respectively) of thelocking element (8) and the locking groove make an angle (A) ofessentially 90° to the upper side of the boards (1, 1′).
 6. A lockingsystem as claimed in claim 5, characterised in that the mechanical means(36, 38) of the locking system which cooperate for vertical locking andthe means (6, 8; 14) of the locking system which cooperate forhorizontal locking have a configuration that allows insertion of thelocking element (8) into the locking groove (14) by inward angling ofone floorboard (1) towards the other floorboard (1′) while maintainingcontact between the joint edge surface portions (41, 42) of the twofloorboards close to the border between the joint plane (F) and theupper side of the floorboards.
 7. A locking system as claimed in claim5, characterised in that the mechanical means (36, 38) of the lockingsystem which cooperate for vertical locking and the means (6, 8; 14) ofthe locking system which cooperate for horizontal locking have aconfiguration which allows insertion of the locking element (8) into thelocking groove (14) by a substantially horizontal motion of onefloorboard (1) towards the other floorboard (1′) during bending of theintegrated strip (6) for snapping in the locking element (8) into thelocking groove (14).
 8. A locking system as claimed in claim 6,characterised in that the mechanical means (36, 38) of the lockingsystem which cooperate for vertical locking and the means (6, 8; 14) ofthe locking system which cooperate for horizontal locking have aconfiguration which allows insertion of the locking element (8) into thelocking groove (14) by a substantially vertical motion of one floorboard(1) towards the other floorboard (1′) during bending of the integratedstrip (6, 8) for snapping in the locking element (8) into the lockinggroove (14).
 9. A locking system as claimed in claim 6, characterised inthat the relationship W>0.5 H, where W=thickness of the locking element(8) parallel with the upper side of the floorboards on a level with theoperative locking surface (19) of the locking element, H=height of thelocking element (8) seen from the upper side of the strip (6).
 10. Alocking system as claimed claim 8, characterised in that therelationship W<5 * H, where W=thickness of the locking element (8)parallel with the upper side of the floorboards on a level with theoperative locking surface (19) of the locking element H=height of thelocking element (8) seen from the upper side of the strip (6).
 11. Alocking system as claimed in claim 8, characterised in that the lockingelement (8) has a thickness parallel with the upper side of thefloorboards which is greater at the lower part of the locking elementthan at its upper part.
 12. A locking system as claimed in claim 8,characterised in that the lower guiding part (12) of the locking groove(14) and the corresponding lower part of the locking element (8) aredesigned so as not to contact each other in the locked position.
 13. Alocking system as claimed claim 8, characterised in that the guidingpart (12) of the locking groove (14) has a portion which is locatedinside a circular arc (C1), which has its centre (C3) where the jointplane (F) intersects the upper side of the floorboards (1, 1′) and whichis tangent to the upper part of the locking element (8).
 14. A lockingsystem as claimed in claim 8, characterised in that the locking element(8) has an upper inclined or rounded guiding part (9) which ispositioned above the operative locking surface (10) of the lockingelement (8) and outside a circular arc (C1), which has its centre (C3)where the joint plane (F) intersects the upper side of the floorboards(1, 1′) and which is tangent to the upper part of the locking element(8).
 15. A locking system as claimed in claim 13, characterised in thatthe sum of on the one hand the horizontal distance (E1) between a loweredge of the guiding part (12) of the locking groove (14) and saidcircular arc (C1) and, on the other hand, the horizontal distance (E2)between an upper edge of the guiding part (9) of the locking element (8)and said circular arc (C1) always exceeds zero, said horizontal distance(E1) for the lower edge of the locking groove being considered negativeif this lower edge is located outside said circular arc (C1).
 16. Alocking system as claimed in claim 13, characterised in that the guidingpart (9) of the locking element (8) and the locking groove (14) aredesigned so as not to contact each other in the locked position.
 17. Alocking system as claimed in claim 14, characterised in that the heightof the locking element (8) and the depth of the locking groove (14) aresuch that the upper part of the locking element in the locked positiondoes not engage the locking groove.
 18. A locking system as claimed inclaim 14, characterised in that the mechanical means (36, 38) of thelocking system which cooperate for vertical locking and the means (6, 8;14) of the locking system which cooperate for horizontal locking have aconfiguration that allows the locking element (8) to leave the lockinggroove (14) in upward angling of the floorboard (1′) having the lockinggroove, while maintaining contact between the joint edge surfaceportions (41, 42) of the two floorboards close to the border between thejoint plane (F) and the upper side of the floorboards.
 19. A lockingsystem as claimed in claim 15, characterised in that the mechanicalmeans (36, 38) of the locking system which cooperate for verticallocking and the means (6, 8; 14) of the locking system which cooperatefor horizontal locking have a configuration that allows the floorboards(1, 1′) to be displaceable parallel with the joint plane (F) in thelocked position.
 20. A locking system as claimed in claim 15,characterised in that the mechanical means (36, 38) for vertical joiningof the floorboards are formed in the joint edge portions (4 a, 4 b) ofthe floorboards.
 21. A locking system as claimed in claim 18,characterised in that the mechanical means (36, 38) for vertical joiningof the floorboards are formed as a tongue-and-groove joint.
 22. Alocking system as claimed in claim 18, characterised in that the strip(6) is made of a material other than that of the core (30) of thefloorboard and is integrally connected with the core.
 23. A lockingsystem as claimed in claim 19, characterised in that the strip is madein one piece with the core (30) of the floorboard and integrallyconnected with the core.
 24. A floorboard having a core (30) andopposing first and second joint edge portions (4 a, 5 a and 4 b, 5 b,respectively), which are designed for joining with adjoining identicalfloorboards by mechanical connection of the first joint edge portion (4a, 5 b) of a first floorboard (1) with the second joint edge portion (4b, 5 b) of an adjoining second floorboard (1′) to a mechanically joinedposition at a vertical joint plane (F), the floorboard having a lockingsystem which comprises a) for vertical joining of the first joint edgeportion (4 a, 5 a) of a first floorboard (1) and the second joint edgeportion (4 a, 5 a and 4 b, 5 b, respectively) of an adjoining secondfloorboard (1′), mechanical cooperating means (36, 38), and b) forhorizontal joining of the first and second joint edge portions (4 a, 5 aand 4 b, 5 b, respectively), mechanical cooperating means (6, 8; 14)which comprise a locking groove (14) formed in the underside (3) of saidsecond floorboard (1′) and extending parallel with and at a distancefrom the vertical joint plane (F) at said second joint edge portion (4b, 5 b) and having a downward directed opening, and a strip (6)integrally formed with the core of said first floorboard (1), whichstrip at said first joint edge portion (4 a) projects from said verticaljoint plane (F) and at a distance from the joint plane (F) has a lockingelement (8) which projects towards a plane containing the upper side ofsaid first floorboard (1) and which has at least one operative lockingsurface (10) for coaction with said locking groove (14), the lockinggroove (14), seen in the plane of the floorboards and away from thevertical joint plane (F) having a greater width than said lockingelement (8), characterised by the combination that said at least oneoperative locking surface (10) of the locking element (8) is essentiallyplane and located at the upper part of the locking element at a distancefrom the upper side of the projecting strip (6) and faces the jointplane (F), that the locking groove (14) has at least one essentiallyplane operative locking surface (11) which is located in the lockinggroove at a distance from the opening of the locking groove and which isdesigned to cooperate with said locking surface (10) of the lockingelement (8) in the joined position, that the locking groove (14) at itslower edge closest to the joint plane (F) has an inclined or roundedguiding part (12) which extends from the locking surface (11) of thelocking groove and to the opening of the locking groove and which isintended to guide the locking element (8) into the locking groove (14)by engaging a portion of the locking element (8) which is positionedabove the locking surface (10) of the locking element or adjacent to itsupper edge, that said operative locking surfaces (10 and 11,respectively) of the locking element (8) and the locking groove (14)make a locking angle (A) of at least 50° to the upper side of theboards.
 25. A floorboard as claimed in claim 24, characterised in thatthe floorboards have a core (30), a surface layer (32) on the upper sideof the core and a balancing layer (34) on the rear side of the core(30).
 26. A floorboard as claimed in claim 24, characterised in that theoperative locking surfaces (10 and 11, respectively) of the lockingelement (8) and the locking groove make an angle (A) of at least 60° tothe upper side of the boards (1, 1′).
 27. A floorboard as claimed inclaim 26, characterised in that the operative locking surfaces (10 and11, respectively) of the locking element (8) and the locking groove makean angle (A) of at least 80° to the upper side of the boards (1, 1′).28. A floorboard as claimed in claim 27, characterised in that theoperative locking surfaces (10 and 11, respectively) of the lockingelement (8) and the locking groove make an angle (A) of essentially 90°to the upper side of the boards (1, 1′).
 29. A floorboard as claimed inclaim 28, characterised in that the mechanical means (36, 38) of thelocking system which cooperate for vertical locking and the means (6, 8;14) of the locking system which cooperate for horizontal locking have aconfiguration that allows insertion of the locking element (8) into thelocking groove (14) by inward angling of one floorboard (1) towards theother floorboard (1′) while maintaining contact between the joint edgesurface portions (41, 42) of the two floorboards close to the borderbetween the joint plane (F) and the upper side of the floorboards.
 30. Afloorboard as claimed in claim 29, characterised in that the mechanicalmeans (36, 38) of the locking system which cooperate for verticallocking and the means (6, 8; 14) of the locking system which cooperatefor horizontal locking have a configuration that allows insertion of thelocking element (8) into the locking groove (14) by a substantiallyhorizontal motion of one floorboard (1) towards the other floorboard(1′) during bending of the integrated strip (6) for snapping in thelocking element (8) into the locking groove (14).
 31. A floorboard asclaimed in claim 29, characterised in that the mechanical means (36, 38)of the locking system which cooperate for vertical locking and the means(6, 8; 14) of the locking system which cooperate for horizontal lockinghave a configuration that allows insertion of the locking element (8)into the locking groove (14) by a substantially vertical motion of onefloorboard (1) towards the other floorboard (1′) during bending of theintegrated strip (6, 8) for snapping in the locking element (8) into thelocking groove (14).
 32. A floorboard as claimed in claim 31,characterised in that the relationship W>0.5 H, where W=thickness of thelocking element (8) parallel with the upper side of the floorboards on alevel with the operative locking surface (19) of the locking element,H=height of the locking element (8) seen from the upper side of thestrip (6).
 33. A floorboard as claimed in claim 31, characterised inthat the relationship W<5 * H, where W=thickness of the locking element(8) parallel with the upper side of the floorboards on a level with theoperative locking surface (19) of the locking element H=height of thelocking element (8) seen from the upper side of the strip (6).
 34. Afloorboard as claimed in claim 33, characterised in that the lockingelement (8) has a thickness parallel with the upper side of thefloorboards which is greater at the lower part of the locking elementthan at its upper part.
 35. A floorboard as claimed in claim 34,characterised in that the lower guiding part (12) of the locking groove(14) and the corresponding lower part of the locking element (8) aredesigned so as not to contact each other in the locked position.
 36. Afloorboard as claimed in claim 35, characterised in that the guidingpart (12) of the locking groove (14) has a portion which is locatedinside a circular arc (C1), which has its centre (C3) where the jointplane (F) intersects the upper side of the floorboards (1, 1′) and whichis tangent to the upper part of the locking element (8).
 37. Afloorboard as claimed in claim 36, characterised in that the lockingelement (8) has an upper inclined or rounded guiding part (9) which ispositioned above the operative locking surface (10) of the lockingelement (8) and outside a circular arc (C1), which has its centre (C3)where the joint plane (F) intersects the upper side of the floorboards(1, 1′) and which is tangent to the upper part of the locking element(8).
 38. A floorboard as claimed in claim 37, characterised in that thesum of on the one hand the horizontal distance (E1) between a lower edgeof the guiding part (12) of the locking groove (14) and said circulararc (C1) and, on the other hand, the horizontal distance (E2) between anupper edge of the guiding part (9) of the locking element (8) and saidcircular arc (C1) always exceeds zero, said horizontal distance (E1) forthe lower edge of the locking groove being considered negative if thislower edge is located outside said circular arc (C1).
 39. A floorboardas claimed in claim 37, characterised in that the guiding part (9) ofthe locking element (8) and the locking groove (14) are designed so asnot to contact each other in the locked position.
 40. A floorboard asclaimed in claim 39, characterised in that the height of the lockingelement (8) and the depth of the locking groove (14) are such that theupper part of the locking element in the locked position does not engagethe locking groove.
 41. A floorboard as claimed in claim 40,characterised in that the mechanical means (36, 38) of the lockingsystem which cooperate for vertical locking and the means (6, 8; 14) ofthe locking system which cooperate for horizontal locking have aconfiguration that allows the locking element (8) to leave the lockinggroove (14) in upward angling of the floorboard (1′) having the lockinggroove, while maintaining contact between the joint edge surfaceportions (41, 42) of the two floorboards close to the border between thejoint plane and the upper side of the floorboards.
 42. A floorboard asclaimed in claim 41, characterised in that the mechanical means (36, 38)of the locking system which cooperate for vertical locking and the means(6, 8; 14) of the locking system which cooperate for horizontal lockinghave a configuration that allows the floorboards (1, 1′) to bedisplaceable parallel with the joint plane (F) in the locked position.43. A floorboard as claimed in claim 42, characterised in that themechanical means (36, 38) for vertical joining of the floorboards areformed in the joint edge portions (4 a, 4 b) of the floorboards.
 44. Afloorboard as claimed in claim 43, characterised in that the mechanicalmeans (36, 38) for vertical joining of the floorboards are formed as atongue-and-groove joint.
 45. A floorboard as claimed in claim 44,characterised in that the strip (6) is made of a material other thanthat of the core (30) of the floorboard and is integrally connected withthe core.
 46. A floorboard as claimed in claim 44, characterised in thatthe strip is made in one piece with the core (30) of the floorboard andintegrally connected with the core.
 47. A locking system for mechanicaljoining of floorboards (1, 1′) having a core (30) and opposite first andsecond joint edge portions (5 a and 5 b, respectively), adjoiningfloorboards (1, 1′) in the mechanically joined position having theirfirst and second joint edge portion (5 a and 5 b, respectively) joinedat a vertical joint plane (F), said joint system comprising a) forvertical joining of the first joint edge portion (5 a) of a firstfloorboard (1) and the second joint edge portion (5 a and 5 b,respectively) of an adjoining second floorboard (1′), mechanicalcooperating means (36, 38), and b) for horizontal joining of the firstand second joint edge portions (5 a and 5 b, respectively), mechanicalcooperating means (6, 8; 14) which comprise a locking groove (14) formedin the underside (3) of said second floorboard (1′) and extendingparallel with and at a distance from the vertical joint plane (F) atsaid second joint edge portion (5 b) and having a downward directedopening, and a strip (6) integrally formed with the core of said firstfloorboard (1), which strip at said first joint edge portion (5 a)projects from said vertical joint plane (F) and at a distance from thejoint plane (F) has a locking element (8) which projects towards a planecontaining the upper side of said first floorboard (1) and which has atleast one operative locking surface (10) for coaction with said lockinggroove (14), the locking groove (14), seen in the plane of thefloorboards and away from the vertical joint plane (F), having a greaterwidth than said locking element (8), characterised by the combinationthat said at least one operative locking surface (10) of the lockingelement (8) is essentially plane and located at the upper part of thelocking element at a distance from the upper side of the projectingstrip (6) and faces the joint plane (F), that the locking groove (14)has at least one essentially plane operative locking surface (11) whichis located in the locking groove at a distance from the opening of thelocking groove and which is designed to cooperate with said lockingsurface (10) of the locking element (8) in the joined position, that theoperative locking surfaces (10 and 11, respectively) of the lockingelement (8) and the locking groove (14) have a locking angle (A) whichis essentially perpendicular to the upper side of the floorboards, thatthe operative locking surfaces (10 and 11, respectively) of the lockingelement (8) and the locking groove (14) have a height (LS) parallel withthe joint plane (F) which is less than 0.5 times the height (H) of thelocking element (8), that the locking groove (14) at its lower edgeclosest to the joint plane (F) has an inclined or rounded guiding part(13) which extends from the locking surface (11) of the locking grooveand to the opening of the locking groove, and that the locking element(8) at its upper end has an inclined or rounded guiding part (9)extending from the operative locking surface (10) of the locking elementand adapted to engage with the guiding part (12) of the locking grooveduring guiding of the locking element (8) into the locking groove (14).48. A locking system as claimed in claim 47, characterised in that thesum of on the one hand the horizontal distance (E1) between a lower edgeof the guiding part (12) of the locking groove (14) and a circular arc(C1), which has it centre (C3) where the joint plane (F) intersects theupper side of the floorboards (1, 1′) and which is tangent to the upperpart of the locking element (8) and, on the other hand, the horizontaldistance (E2) between an upper edge of the guiding part (9) of thelocking element (8) and said circular arc (C1) always exceeds zero, saidhorizontal distance (E1) for the lower edge of the locking groove beingconsidered negative if this lower edge is located outside said circulararc (C1).
 49. A locking system as claimed in claim 48, characterised inthat the floorboards (1, 1′) have a core (30), a surface layer (32) onthe upper side of the core and a balancing layer (24) on the rear sideof the core (30).
 50. A locking system as claimed in claim 49,characterised in that the mechanical means (36, 38) of the lockingsystem which cooperate for vertical locking and the means (6, 8; 14) ofthe locking system which cooperate for horizontal locking have aconfiguration that allows insertion of the locking element (8) into thelocking groove (14) by a substantially horizontal motion of onefloorboard (1) towards the other floorboard (1′) during bending of theintegrated strip (6) for snapping in the locking element (8) into thelocking groove (14).
 51. A locking system as claimed in claim 50,characterised in that the lower guiding part (12) of the locking groove(14) and the corresponding lower part of the locking element (8) aredesigned so as not to contact each other in the locked position.
 52. Alocking system as claimed in claim 51, characterised in that the lockingelement (8) has an upper guiding part (9) which is positioned above theoperative locking surface (10) of the locking element (8) and furtheraway from said centre (C3) than the circular arc (C1) which is tangentto the upper end of the locking element (8).
 53. A locking system asclaimed in claim 52, characterised in that the guiding part (9) of thelocking element (8) and the locking groove (14) are designed so as notto contact each other in the locked position.
 54. A locking system asclaimed in claim 53, characterised in that the height of the lockingelement (8) and the depth of the locking groove (14) are such that theupper part of the locking element in the locked position does not engagewith the locking groove.
 55. A locking system as claimed in claim 54,characterised in that the mechanical means (36, 38) of the lockingsystem which cooperate for vertical joining and the means (6, 8; 14) ofthe locking system which cooperate for horizontal joining have aconfiguration that allows the floorboards (1, 1′) to be displaceableparallel with the joint plane (F) in the locked position.
 56. A lockingsystem as claimed in claim 55, characterised in that the mechanicalmeans (36, 38) for vertical joining of the floorboards are formed in thejoint edge portions (5 a, 5 b) of the floorboards.
 57. A locking systemas claimed in claim 56, characterised in that the mechanical means (36,38) for vertical joining of the floorboards are formed as atongue-and-groove joint.
 58. A locking system as claimed in claim 52,characterised in that the strip is made of a material other than that ofthe core (30) of the floorboard and is integrally connected with thecore.
 59. A locking system as claimed claim 58, characterised in thatthe strip is made in one piece with the core (30) of the floorboard andintegrally connected with the core.
 60. A floorboard comprising a core(30) and opposite first and second joint edge portions (5 a and 5 b,respectively) which are designed for joining with adjoining floorboardsby mechanical connection of the first joint edge portion (5 a) of afirst floorboard (1) with the second joint edge portion (5 b) of anadjoining second floorboard (1′) to a mechanically joined position at avertical joint plane, the floorboard having a locking system whichcomprises a) for vertical joining of the first joint edge portion (5 a)of a first floorboard (1) and the second joint edge portion (5 a and 5b, respectively) of an adjoining second floorboard (1′), mechanicalcooperating means (36, 38), and b) for horizontal joining of the firstand second joint edge portions (5 a and 5 b, respectively), mechanicalcooperating means (6, 8; 14) which comprise a locking groove (14) formedin the underside (3) of said second floorboard (1′) and extendingparallel with and at a distance from the vertical joint plane (F) atsaid second joint edge portion (5 b) and having a downward directedopening, and a strip (6) integrally formed with the core of said firstfloorboard (1), which strip at said first joint edge portion (5 a)projects from said vertical joint plane (F) and at a distance from thejoint plane (F) has a locking element (8) which projects towards a planecontaining the upper side of said first floorboard (1) and which has atleast one operative locking surface (10) for coaction with said lockinggroove (14), the locking groove (14), seen in the plane of thefloorboards and away from the vertical joint plane, (F) having a greaterwidth than said locking element (8), characterised by the combinationthat said at least one operative locking surface (10) of the lockingelement (8) is essentially plane and located at the upper part of thelocking element at a distance from the upper side of the projectingstrip (6) and faces the joint plane (F), that the locking groove (14)has at least one essentially plane operative locking surface (11) whichis located in the locking groove at a distance from the opening of thelocking groove and which is designed to cooperate with said operativesurface (10) of the locking element (8) in the joined position, that theoperative locking surfaces (10 and 11, respectively) of the lockingelement (8) and the locking groove (14) have a locking angle (A) whichis essentially perpendicular to the upper side of the floorboards, thatthe operative locking surfaces (10 and 11, respectively) of the lockingelement (8) and the locking groove (14) have a height (LS) parallel withthe joint plane (F) which is less than 0.5 times the height (H) of thelocking element (8), that the locking groove (14) at its lower edgeclosest to the joint plane (F) has an inclined or rounded guiding part(12) which extends from the locking surface (11) of the locking grooveand to the opening of the locking groove, and that the locking element(8) at its upper end has an inclined or rounded guiding part (9)extending from the operative locking surface (10) of the locking elementand adapted to engage with the guiding part (12) of the locking grooveduring guiding of the locking element (8) into the locking groove (14).61. A floorboard as claimed in claim 60, characterised in that the sumof on the one hand the horizontal distance (E1) between a lower edge ofthe guiding part (12) of the locking groove (14) and a circular arc(C1), which has it centre (C3) where the joint plane (F) intersects theupper side of the floorboards (1, 1′) and which is tangent to the upperpart of the locking element (8) and, on the other hand, the horizontaldistance (E2) between an upper edge of the guiding part (9) of thelocking element (8) and said circular arc (C1) always exceeds zero, saidhorizontal distance (E1) for the lower edge of the locking groove beingconsidered negative if this lower edge is located outside said circulararc (C1).
 62. A floorboard as claimed in claim 61, characterised in thatthe floorboards (1, 1′) have a core (30), a surface layer (32) on theupper side of the core and a balancing layer (24) on the rear side ofthe core (30).
 63. A floorboard as claimed in claim 62, characterised inthat the mechanical means (36, 38) of the locking system which cooperatefor vertical locking and the means (6, 8; 14) of the locking systemwhich cooperate for horizontal locking have a configuration that allowsinsertion of the locking element (8) into the locking groove (14) by asubstantially horizontal motion of one floorboard (1) towards the otherfloorboard (1′) during bending of the integrated strip (6) for snappingin the locking element (8) into the locking groove (14).
 64. Afloorboard as claimed in claim 63, characterised in that the lowerguiding part (12) of the locking groove (14) and the corresponding lowerpart of the locking element (8) are designed so as not to contact eachother in the locked position.
 65. A floorboard as claimed in claim 64,characterised in that the height of the locking element (8) and thedepth of the locking groove (14) are such that the upper part of thelocking element in the locked position does not engage with the lockinggroove.
 66. A floorboard as claimed in claim 65, characterised in thatthe mechanical means (36, 38) of the locking system which cooperate forvertical joining and the means (6, 8; 14) of the locking system whichcooperate for horizontal joining have a configuration that allows thefloorboards (1, 1′) to be displaceable parallel with the joint plane (F)in the locked position.
 67. A floorboard as claimed in claim 66,characterised in that the mechanical means (36, 38) for vertical joiningof the floorboards are formed in the joint edge portions (5 a, 5 b) ofthe floorboards.
 68. A floorboard as claimed in claim 67, characterisedin that the mechanical means (36, 38) for vertical joining of thefloorboards are formed as a tongue-and-groove joint.
 69. A floorboard asclaimed in claim 68, characterised in that the strip (6) is made of amaterial other than that of the core (30) of the floorboard andintegrally connected with the core.
 70. A floorboard as claimed in claim60, characterised in that the strip is made in one piece with the core(30) of the floorboard and integrally connected with the board.
 71. Aflooring formed by joining floorboards according to claim 70.